Directions: Express answers to the correct number of significant figures. Show all work.

5. Which of the following represent isotopes of the same element? : 34 B: 79x C: 78x 34 D: 81x 35 36 A) A and D B) A and C C) B and D D) C and D 6. In which of the following sets do all species have the same number of electrons? A) CF, Ar, Ca2+ ) , N3-, 02- C) K+, Rb+, Cs+ D) Br, Br, Br+ 7. In which of the following sets do all species have the same number of protons? A) F-, Ne, Mg2+ B) C, N3-, 02- C) Sr2+, Ba2+, Ra2+ D) S, s2-, s2+